PERFORMANCE CHARACTERISTICS OF EMP POWER & SIGNAL FILTERS
EMP PROTECTION CLASS A
Power cables are protected by gas-gap type arrestors which are mounted in filter cabinets.
The connecting wires of arrestors are as short as possible and unnecessary bends are
avoided. Each gas-gap is provided for one conductor.
The characteristics of gas-gaps are as follows:
Nominal voltage: 220VAC, 50 Hz
Pulse spark over voltage: Less than 2000V, against wave with both polarity having the
rising rate of 10KV/micro second.
Spark over voltage: Not less than 500 V (RMS)
Max. instantaneous current capacity: 65 KA minimum.
Discharge voltage: At 10 x 20 micro second wave, maximum 3 KV for 40 KA.
The low-pass filters normally used for control cables are protected against pulses by MOV
(Metal oxide varistor) elements. The specifications are as follows:
- MOV's are provided for each conductor and connected to cabinet ground.
- Rated voltage: 120VAC or 24V DC
- Max. current: 2500 A - for the waves with the duration time less than 20 micro second.
EMP PROTECTION CLASS B
in addition to the low-pass filters, cables are protected by gas-gap type arrestors. The
specifications are as follows:
- DC insulation breakdown voltage: 250 - 500 VDC.
- Pulse spark over voltage: Less than 1000 V at 10 KV/micro second.
- Operational life: 1000 break.
In addition to the gas-gap type arrestors, zener diodes are used for the protection of the communication
cables. The diodes are mounted in the cabinet on the equipment side. The diodes have power rating of 5 W and operate at 200 V DC. For each filter double diodes are used and are connected anode to anode or cathode to cathode.